Thanks to Google, hundreds of millions of people are today celebrating Hans Christian Ørsted’s birthday without having much of a clue who he is â€¦ so who exactly was he? … Probably not even the physics geeks remember much about Hans Christian Ørsted, although Google’s Doodle logo illustrates his key discovery. That is, if you run a current through a wire â€“ in this case, from the battery at the front â€“ then the electricity creates a magnetic field, which will deflect a compass needle. Thus the study of electromagnetism was born, and it’s the basis of a lot of modern life: it led to the development of electricity generators and transformers. Remember that next time you flick a light switch.